Really, that's what it boils down to. We don't HAVE to sin. Very seldom does someone hold a gun to our head and force us to sin; and even then, as the martyrs have shown us, there is still a choice.
So just think about that. Every temptation is a choice. That means you have as much freedom to say "No" as you do opportunity to say "Yes."
We don't have to live life on automatic. We can choose. Got a bad habit? Remember: each incidence, each temptation, is a choice. You don't have to break the whole habit. You just have to make the right choice that time. The next time, it will be easier.
Every temptation is a choice.